The invention relates to tunable lasers. In particular, the invention relates to a crystalline material for a tunable solid state laser formed of a yttrium aluminum garnet (YAG) host and a trivalent manganese dopant.
It is known that transition metal ions in insulating crystal hosts support lasing. Indeed, the first laser to be demonstrated, namely ruby, is an example of a Cr.sup.3+ ion in an Al.sub.2 O.sub.3 host. More recently, a system incorporating Ti.sup.3+ :Al.sub.2 O.sub.3 (Ti:sapphire) has received much attention and has been developed into a widely tunable laser covering the wavelength range from 0.69 to 1.1 .mu.m. The other major category of solid-state lasers is based on a yttrium aluminum garnet (YAG) host doped with rare earth ions, most notably Nd:YAG. In contrast to many transition-metal solid-state lasers, rare earth lasers are not widely tunable.
The luminescence properties of divalent manganese have been investigated extensively, particularly in MnF.sub.2, which has been used as a host for other transition-metal ions, but data on trivalent and higher oxidation states of manganese in insulating crystals are very scarce.
Of all commercially successful solid-state lasers, the shortest-wavelength operation is achieved in Ti:sapphire at the red edge of the visible spectrum, 0.69 .mu.m. Currently there are no tunable solid state lasers operative in the yellow-orange spectral range (0.59-0.63 .mu.m). These wavelengths are not covered by existing tunable lasers, except for dye lasers in the visible. Solid-state lasers are more desirable sources because of their high output power, reliability and ease of operation. The YAG host material has the advantage that it is the most highly developed laser crystal available. The crystal growth of YAG has reached a highly sophisticated stage, with large-diameter crystals of good optical quality being commercially available. The thermal conductivity and fracture strength of YAG are high, making it an ideal host for high output lasers.
It is an object of the present invention to provide a tunable solid state laser suitable for broad band operation in selected wavelengths of interest.